For children between the ages of 3 and 5, their "readiness" to function competently in school is best understood in terms of the nature and quality of their interactions in classrooms with adults, with peers, and with learning/instructional activities. Classroom interactions provide perhaps the most valid indicator of the manner in which children make use of the learning and social opportunities provided in school. The principal aim of the project is to develop, field-test, and validate an observational assessment of young children's social, emotional and task-oriented competence as displayed in early education classrooms with peers, teachers, and instructional activities (The Classroom Assessment Scoring System-Child Version) that can be used by teachers, researchers, and evaluators in at-scale applications. The assessment will consist of behavioral indicators scaled in terms of age (3-5 years) that are organized into global rating scales for key competencies. In the first year, we plan to use a large archive of more than 1,000 hours of videotape footage from over 200 classrooms (of 3, 4, and 5 year olds) to identify developmentally appropriate behavioral indicators for competencies in the domains of task-orientation (e.g., engagement, persistence), self-regulation (e.g., self-reliance, behavioral and emotional regulation), relationships with peers (e.g., cooperation; positive sociability), relationships with teacher (e.g., closeness; conflict), and social communication (e.g., initiation, use of language for problem solving). In the first and second years we conduct a series of pilot studies using live observation of 6 children in each of 70 classrooms to finalize behavioral indicators and rating scales. Years 3 and 4 involve a short-term longitudinal validation study of 600 3-, 4-, and 5-year old children in 100 classrooms in which the observational indicators will be scaled for growth trajectories and correlated with direct assessments of academic performance and teachers' reports of children's competence. In year 5 we will conduct a reliability study involving teachers' use of the observational system. Throughout the project period we will develop and field-test training materials and reliability procedures that can be applied in real-world, at-scale applications; for example we will develop a web-based training and reliability protocol that can be used successfully by preschool teachers. The resulting measurement system will provide observationally based assessment of children's competence in classroom interactions with adults, peers, and activities, with growth scaled over the 3-5 age span, that is applicable to demands of large-scale assessments. As such, the assessment will meet a basic public health need to describe individual children's competencies in a manner that is sensitive to intervention.